(a) Technical Field
The present invention relates to a fuel cell with a porous material-gasket integrated structure. More particularly, the present invention relates to a fuel cell having a porous material-gasket integrated structure stacked on a separator, in which a porous material and a gasket are integrally molded. The thus formed structure facilitates the flow of gas and water through the fuel cell.
(b) Background Art
The configuration of a unit cell of a typical fuel cell stack will be described with reference to FIG. 8. A membrane electrolyte assembly (MEA) is positioned in the center of the unit cell. The membrane electrolyte assembly includes a polymer electrolyte membrane 10 capable of transporting hydrogen ions (protons), and catalyst layers such as a cathode 12 and an anode 14. The catalyst layers are coated on both sides of the electrolyte membrane 10 such that hydrogen and oxygen react with each other.
As shown, a gas diffusion layer (GDL) 16 is stacked on the outside of each of the cathode 12 and the anode 14. A separator 20, in which flow fields are formed to supply fuel and discharge water produced by a reaction, is stacked between the gas diffusion layer 16 and a gasket 18, and an end plate 30 for supporting and fixing the above-described components is connected to the outermost side end.
Accordingly, at the anode 14 of the fuel cell stack, an oxidation reaction of hydrogen occurs to produce hydrogen ions (protons) and electrons, and the produced hydrogen ions and electrons are transmitted to the cathode 12 through the electrolyte membrane 10 and the separator 20. At the cathode 12, the hydrogen ions and electrons transmitted from the anode 14 react with the oxygen-containing air to produce water. At the same time, electrical energy is generated by the flow of electrons, and the electrical energy is supplied to a load requiring the energy through a current collector connected to the end plate 30.
In the above-described fuel cell, water that is produced is not smoothly discharged on a reaction surface of the separator 20, which is in contact with the anode 14 and the cathode 12, respectively. As a result, a flooding phenomenon occurs and, at the same time, the flow fields of the separator 20 are clogged, which are very problematic.
One proposed method for addressing these drawbacks is shown in FIG. 7, in which a fuel cell is provided with a separate porous material 40 interposed between a membrane electrode assembly 50 and a separator 20 to facilitate the flow of gas and water.
However, the porous material 40 is separately applied over a flow region of a fuel, i.e., a region between the anode and the separator and a region between the cathode and the separator. While the porous material 40 serves as a flow field, it increases the number of layers that constitute the fuel cell, thus increasing the length and thickness of the fuel cell stack.
Moreover, since the porous material 40 is separately applied over a wide range of reaction regions, the heat transfer efficiency for transferring heat to the exterior of the fuel cell during heat dissipation is reduced. This can cause overheating of the fuel cell stack, thus deteriorating the performance of the fuel cell stack.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not establish a prior art that is already known in this country to a person of ordinary skill in the art.